diff --git a/wp-includes/media.php b/wp-includes/media.php
index 57037710b0..c232d8e6a3 100644
--- a/wp-includes/media.php
+++ b/wp-includes/media.php
@@ -693,23 +693,35 @@ function get_intermediate_image_sizes() {
  * @return false|array Returns an array (url, width, height), or false, if no image is available.
  */
 function wp_get_attachment_image_src( $attachment_id, $size = 'thumbnail', $icon = false ) {
-
 	// get a thumbnail or intermediate image if there is one
-	if ( $image = image_downsize($attachment_id, $size) )
-		return $image;
+	$image = image_downsize( $attachment_id, $size );
+	if ( ! $image ) {
+		$src = false;
 
-	$src = false;
+		if ( $icon && $src = wp_mime_type_icon( $attachment_id ) ) {
+			/** This filter is documented in wp-includes/post.php */
+			$icon_dir = apply_filters( 'icon_dir', ABSPATH . WPINC . '/images/media' );
 
-	if ( $icon && $src = wp_mime_type_icon($attachment_id) ) {
-		/** This filter is documented in wp-includes/post.php */
-		$icon_dir = apply_filters( 'icon_dir', ABSPATH . WPINC . '/images/media' );
+			$src_file = $icon_dir . '/' . wp_basename( $src );
+			@list( $width, $height ) = getimagesize( $src_file );
+		}
 
-		$src_file = $icon_dir . '/' . wp_basename($src);
-		@list($width, $height) = getimagesize($src_file);
+		if ( $src && $width && $height ) {
+			$image = array( $src, $width, $height );
+		}
 	}
-	if ( $src && $width && $height )
-		return array( $src, $width, $height );
-	return false;
+	/**
+	 * Filter the image src result
+	 *
+	 * @since 4.3.0
+	 *
+	 * @param array|false   $image          Either array with src, width & height, icon src, or false.
+	 * @param int           $attachment_id 	Image attachment ID.
+	 * @param string|array  $size           Optional. Registered image size to retrieve the source for or a flat
+	 *                                      array of height and width dimensions. Default 'thumbnail'.
+	 * @param bool          $icon           Optional. Whether the image should be treated as an icon. Default false.
+	 */
+	return apply_filters( 'attachment_image_src', $image, $attachment_id, $size, $icon );
 }
 
 /**
diff --git a/wp-includes/version.php b/wp-includes/version.php
index 7553c7da27..4d7da56819 100644
--- a/wp-includes/version.php
+++ b/wp-includes/version.php
@@ -4,7 +4,7 @@
  *
  * @global string $wp_version
  */
-$wp_version = '4.3-alpha-32865';
+$wp_version = '4.3-alpha-32866';
 
 /**
  * Holds the WordPress DB revision, increments when changes are made to the WordPress DB schema.